Bore hole detector and firing apparatus



July 26, 1960 M. M. HAWTHORNE 2,946,926

BORE HOLE DETECTOR AND FIRING APPARATUS Filed March 6, 1958 CONTROL 95 STATION 55 59 85 "llllll s ""'ggngw 1 i 7 85 i 8i 89 ng. 2 95 VOLTAGE SOURCE BORE HOLE DETECTOR AND FIRING APPARATUS Millo Marion Hawthorne, Fort Worth, Tex., assigner to Go Oil Well Services, Inc., Fort Worth, Tex.

Filed Mar. 6,1958, Ser. No. 719,543

y8 Claims. (Cl. 317-80) My invention relates to apparatus for detecting casing collars or other anomalies in bore holes and apparatus for firing casing perforating devices in bore holes, and particularly to such apparatus wherein electric circuitry is employed and the said detecting and firing apparatus uses a common electric transmission channel. v

lt is common practice in the petroleum industry to lower perforating devices into a bore hole or well and to tire such devices to make openings in the well casing and surrounding formation to allow oil to flow into the well. Such perforating devices are of either the shaped charge, or jet type; or the bullet type, both of which are well known in the art. It is usually desirable that the perforations be made at an accurately determined depth in the well. One method of making accurate well depth measurements is to lower a device known as a casing collar4 locator, which transmits an identifying signal via a transmission line to the above ground control station as each casing collar is passed. By counting the casing collars passed, there being a known standard spacing between them, the depth ofthe collar locator in the well at any time can be `readily determined. When the perforating devices are lowered to the desired depth as determined by the casing collar locator, they are detonated by transmission of an electric signal from the control station above ground via a transmission ,line down the bore hole to a detonator device, such as a blasting cap, which is associated with the perforating devices. It is desirable to lower the casing collar locator and the perforating devices into the well by means of a wire line or cable, and to use the cable also as a commonV transmission line both for the casing collar locator signals and for the perforating device detonator signal. Use of the cable as a common transmission line involves a number of problems. The casing collar locator requires a relatively high impedance winding in order to generate a satisfactory output signal. One the other hand, the impedance of the detonator device is relatively low. Consequently, if the collar locator and detonator circuits were connected in series, the high impedance of the collar locator would necessitate use of -an undesirably high voltage detonator signal. If the two circuits were connected in parallel, then a substantial portion of the signal generated by the collar locator would be shunted to ground via the detonator circuit. One important consideration is that of safety. In some prior art devices it is possible to actuate the detonator device by application of a relatively low voltage impulse on the transmission line, and accidental application of suchvoltage could have disastrous consequences. A number of proposals for the solution of the foregoing problems have been advanced, but `none have proved to be entirely satisfactory.

It is accordingly an object of my invention to provide apparatus and circuits to effect satisfactory solutions for the problems aforementioned.

Another object of my invention is to provide improved apparatus and circuits to allow employment of a common transmissionline for collar locator and detonator circuits.

.2 Another object of my invention is to provide an improved system and apparatus including a detonator circuit and a collar locator circuit utilizing a common trans- V mission line, and wherein neither circuit is undesirably affected by the other.

Another object of my invention is to provide an improved system and apparatus including a detonator circuit and a casing collar locator circuit utilizing a common transmission line, said system and apparatus being more rugged and dependable than those of prior art.

Another object of my invention is to provide an improved system and apparatus including a detonator cir` cuit and a casing collar locator circuit utilizing a common transmission line, with said system incorporating a high degree of safety.

These and other objects are effected by my invention as will be apparent from the following description taken in accordance with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a longitudinal section view of a casing collar locator assembly in accordance with a preferred embodiment of the invention;

Fig. 2 is an end elevational view of the device of Fig. l;

Fig. 3 is a schematic circuit diagram; and

Fig. 4 is a diagrammatic showing of the collar locator and perforating assembly in position in a bore hole.

Referring Vnow to the drawings, and particularly to Figures 1 and 2, there is shown a casing collar locator assembly 11 including a housing 13, upper and lower housing end closures 15, 17, a transformer core 19, transformer primary and secondary windings 21, 23, upper and lower permanent magnets 25, 27, upper and lower magnet pole pieces 29, 31, upper and lower connector receptacles 33, 35, and upper and lower receptacle covers 37, 39. The transformer core 19 is in the form of a spool of soft iron material. Each permanent magnet 25, 27 is in the form of a short solid cylinder having an axial opening therein. Each pole piece 29, 31 is in the form of a short solid soft iron disk having a cylindrical recess 41 centered on one side thereof. Each receptacle cover 37, 39 is a hollow cylinder of insulating material, closed at one end. Each receptacle 33, 35 is a metal cylinder having an axial opening therein. The housing 13 is a relatively thick-walled hollow cylinder of non- -magnetic material, such as brass, or stainless steel, having a smooth portion 43 of slightly increased inside diameter adjacent to and extending to each end portion, and having female threads 45 extending inwardly from each smooth portion for a short distance. Each end closure 15, 17 is in the form of a cylindrical plug having male threads 47 at its inner end portion which are adapted to be received by the female threads 45 of housing 13. Immediately outwardly from the male threads are a pair of sealing ring grooves 49. Forming a part of one wall of the outermost groove is a radial surface 51 adapted for abutting the end of the housing. Extending outwardly from the radial' surface is a peripheral cylindrical surface 53 having diameter the same as the outer diameter of the housing. Extending from the cylindrical surface just mentioned to the outer end of the end closure is an inwardly tapering frustro-conical surface 55. The end closure 15, 17 has an axial bore of diameter equal to the outside diameter of the receptacle cover 37, 39. The right end portion of the end closure bore is threaded, and there is a sealing ring groove 57 at the inner end ofthe threads 59.V Both upper and lower magnets 25, 27, pole pieces 29, 31, receptacle covers 37, 39, receptacles 33, 35, land housing end closures 15, 17, are respectively 'substantially identical. When the collar locator device is assembled, the housing, housing end closures, receptacles, receptacle covers, pole pieces,vmagnets, and core, all have lystated, the receptacle cover outside diameter equals thev end Closure inside diameter, and also the diameter of the pole piece cylindrical recess. The outside diameter of the receptacle equals the inside diameter of the receptacle cover.

Injassembly of the collar locator device, the magnets 25, 27 tare placedV one at each end of the core 19, with one face ofthe respective magnet abutting a respective end face of the core spool, and are then soldered to the core, with like poles of the magnets adjacent. Next, the planar 'faces of the pole pieces 29, 31 are placed in abutting'relation to the respective other magnet face and soldered to the magnet. Next, a radial hole 61 is drilled in each pole piece from its outer surface through the Wall of the cylindrical recess 11,-and then a groove 63 is milled on the outer surface from the hole to the respective pole piece inner face. Also, a hole 65 is drilled in each ange of thecore 19, communicating from the center portion ofthe ilange outer surface to the bottom of the respective ange inner face, and then a groove 67 is milled on the respective ange outer surface from the hole to the respectiveflange outer face. Next, the transformer secondary 23 is Wound on the core, and then the transformer primary 21. One end of the secondary winding 23 is 'groundedto the core 19 and the other end brought out through the opening 65 in the core lower flange, then into the openin-g 61 in the lower pole piece 31 and out at the pole piece cylindrical recess 41. One

Y Thus the adapter 89 serves the dual purpose of mechaniend of the primary winding 21 is grounded to the core 19 and the other end is brought out through the opening 46,5? in the core upper flange, then into the opening 61 in the upperV pole piece 29 and out at the pole piece cylindrical recess 41. Next, the respective receptacle holder 37, 39 is placed with its closed end in the respec- Y tive pole piece cylindrical recess 41 and fixed thereto by means of a screw 69 rwhich passes through an opening in the cover end and threads into the pole piece. Each receptacle holderalso has a radial opening in its side for receiving a screw 71, Vand a groove 73 on its outer surface extending from the opening to the inner end of the cover. The respective receptacle 33, has a threaded radial'opening in its side. Next, the respective receptacle is placed in its cover, and a respective transformer winding terminal is placed under the screw 71 which is passed through the cover side opening and threaded into the Vreceptacle side opening. The screw 71 thus electrically connects the respective transformer Winding terminal to the respective receptacle 33,V 35, and also retains the respective receptacle in place within its cover. Finally, sealing rings 75 are placed in the housing end closure sealing ring grooves 49, and the respective end closure 15, 17 is threaded onto the housing end. The collar locator assembly is now ready for assembly to the other tool components which are to be lowered into the bore hole with it, as will be hereinafter described.

` In Fig. 4 there is shown diagrammatically a tool assembly in a bore hole. The tool assembly includes a bottom nose 77, a perforating section 79, the collar locator assembly 11, and a cable head 81. The cable 83 itself is of a type having an outer sheath 85 and an inner core 87. The outer sheath 85 serves both as a weight carrier and a ground conductor, while the inner core 87 is an electrical' conductor. The cable S3 is fixed to a conventional cable head 81, wi'thjthe4 inner core terminating in a female receptacle within the cable head. The cable head is fixed to the collar locator by means of an adapter Orcoupler 89 having male threads on each end'which thread' into the female threads of the cable'head and the collar locator, and having a banana pluggextending outward beyond each end andV received respectively by the receptaclesdof the collar locator and the cable head.

cally and electrically coupling the collar locator to the cable head. Likewise, `an adapter is employed to couple the collar locator 11 to the perforator .section 79, and another to couple the perforating section 79 to the bottom nose 77. In each case the adapter compresses sealing rings, as for example, one in the groove 57 at the end of the collar locator end closure femaleV threads, so that the entire tool assembly is completely sealed. Fig. 4 also shows a typical casing collar 91 joining adjacent casing sections 93, 95. The tool assembly is lowered into the bore hole by the cable 83 which is reeled off a conventional powered drum arrangement (not shown). Located above ground, usually in a mobile vehicle, is a control station 95, which is represented as a block in Fig. 4. insofar as is pertinent to the present invention, the control station includes means for selectively connecting to the common transmission line a suitable indicator device to receive signals from the collar locator, or a voltage source from which the perforating section detonating signals are derived.

Y Fig. 3 shows in schematic form, an electric circuitry arrangement utilizing my invention. A selector switch 97 has its common terminal 99 connected to a conductor 87 which may be considered as the core of the cable, or common transmission line, the lower end o-f which is connected in series with the transformer primary winding 21 to ground 101. The transformer secondary winding 23 has one end connected to ground 101 and the other end connected through the perforating section detonator device, represented by an impedance 103, to ground 101. One pole 105 of selector switch is connected through an indicator device 107 to ground 101, while the other pole 109 of the selector switch 97 is connected through a voltage source 111 to ground 101.

In operation, the magnets 25, 27-produce magnetic elds having ilux'paths which include the core 19, the pole pieces 29, 31, and the bore hole casing. The collar locator housing 13, being made of non-magnetic material, has little or no effect on the magnetic iields. The collar locator 1l depends for its operation on current which is induced in the transformer winding 21 as a result of magnetic flux path changes or disturbances. The magnitude of induced current depends both on .the nature or extent of the ux path change and upon the rate of the change. `Since the collar locator is arranged with a magnet at each end of the clore, and with like poles adjacent, changes in the flux path due to sideways or lateral motion of the collar locator Within the bore hole casing are balanced out or cancelled, so that nocurrent is induced in the transformer windings as result of such motion. Flux path changes due to longitudinal motion of the collar locator in the casing, however, are not balanced out. Therefore, if the collar locator is being raised or lowered within the casing and approaches some anomaly, such as increased casing wall thickness, there will be a flux path change which causes current to be induced in the transformer windings. The anomaly which the collar locator is designed to sense is that caused by the occurrence of a casing collar, and may include the collar bulge as well as the casing joint gap. In practice, the transformer primary winding 21 will produce a small pulse of Vcurrent as the Ycollar locator is raised or lowered past a collar. The ratio of primary to secondary turns is made suiciently high that very little .of the available energy is dissipated in the secondary 23, and there fore most of it is utilized bythe primary 21 to generate a signal for transmission to the indicator device 107 at the control station 95., I have found in practice that a winding ratio of about twelve to one is satisfactory. Specicially, I wind about a thousand turns of number 25 wireV for the secondary 23, andV about twelve thousand turns of number 28 wire for the primary 21. vSince the amperes, there is no danger that the small portion generated in the secondary could ever be sufficient to actuate the perforating section detonator 103. Thus, when it is desired to lower the tool assembly into the bore hole to a given depth, the selector switch 97 is closed to the indicator circuit pole 105, and as the assembly is lowered there is transmitted to the indicator 107 a signal pulse as each casing collar is passed. The indicator may be a microammeter, galvanometer, or suitable record device. When the tool assembly has been lowered to the desired depth as determined by the number of casing collars passed, the selector switch 97 is moved to the detonator signal pole 109. The detonator signal may be a series of alternating current pulses, or it may be a single pulse such as would be obtained from a condenser discharge. yIn practice I have found a seri of 110 volt 60 cycle alternating current impulses to be satisfactory, and also a single pulse from a 40 microfarad condenser charged to 250 volts. The detonator pulses appear in the transformer secondary 23 as pulses reduced to about 1/12 their original voltage, that is, in the range from approximately 7 to 2O volts, which is sufficient for positive actuation of the perforating section detonator 103.

It will be apparent from the foregoing that I have provided a simple and effective collar locator device and arrangement which utilizes a common transmission line for transmitting collar locator signals from the tool assembly to the control station and for transmitting the detonating signals from the control stationl to the tool assembly. I have found the device and arrangement of my invention to be dependable, durable, and trouble free. While I have described my invention as used in connection with perforating devices, it is to be understood that this was done by way of example only, and that my invention can also be used and is intended for use in connection with bridge plugs, dump bailers, and other devices wherein an action is initiated by a detonator v device. It should also be pointed out that the system and arrangement of my invention incorporates a high degree of safety in that accidental detonation is made very unlikely because of the relatively high voltage that must be applied to the line to accomplish detonation. This Voltage is as much as thirty times the voltage required for detonation in some prior art arrangements.

While I have shown my invention in only one form, it will be obvious to those skilled in the art that it is not so limited but susceptible of various changes and modification Without departing from the spirit thereof.

I claim:

1. In an arrangement for performing operations in cased bore holes wherein there is provided a collar locating device and a detonator assembly suspended in the hole by means of a cable; and a control station aboveground, with the cable constituting a single transmission channel, with the control station including an indicator device adapted for receiving signals from said collar locator device, a source of detonator signals, and means for selectively connecting either said indicator device or said source to said cable transmission channel; with said detonator assembly including an electrically actuable detonator device; and with said collar locating device including a relatively high inductance element in which signals are induced responsive to casing anomalies; that improvement comprising a relatively low inductance element magnetically linked to said relatively high inductance element, conductors connecting said relatively high inductance element in series with said cable transmission channel, and conductors connecting said relatively low inductance element in series with said detonator device. g

2. In an arrangement for performing operations in cased bore holes wherein there is provided a collar locating device and a detonator assembly suspended in a hole by a cable; and a control station above ground, with a cable constituting a single electrical transmission channel, with the control station including an indicator device adapted for receiving signals from the collar locator device, a source of detonator signals, and means for selectively connecting said indicator device or said source to said cable -transmission channel; with said detonator assembly including an electrically responsive detonator de` vice; and with said collar locating device including the rst -inductance element for generating signals responsive to the occurrence of casing anomalies; that improvement comprising a second inductance element magnetically linked to said first inductance element; conductors connecting said first inductance element in series with said cable transmission channel, and conductors connecting said second inductance element in series with said detonator device.

3. In an arrangement for performing operations in cased bore holes wherein there is provided a collar locating device and a detonating assembly suspended in a hole by a cable; and a control station aboveground, with a cable constituting a two-conductor transmission channel, one conductor of which is comm-on, with the control station including an indicator device adapted for receiving signals from said collar locator device, a source of detonator signals, and means for selectively connecting either said indicator device or said source to said cable transmission channel; with said detonator assembly including an electrically `actuable detonator device; that improvement wherein said collar locating device includes a transformer having a relatively high inductance primary winding in which signals are induced responsive `to casing anomalies, and a relatively low inductance secondary winding, conductor means connecting said primary winding between the common conductor of said cable trans-V mission line and its other conductor, and conductor means connecting one side of said secondary winding to common and the other side of said secondary winding in series with said detonator device and then to common.

4. In an arrangement for performing operations in cased bore holes wherein there is provided a collar locating device and a detonator assembly suspended in a hole by a cable; and a control station aboveground, with the cable constituting a single conductor transmission channel, with the control station including an indicator device adapted for receiving signals, and means for selectively connecting either said indicator device 'or said source to said cable transmission channel; with said detonating assembly including an electrically actuable detonator device; that improvement wherein said collar locating device includes a step-down transformer having a primary winding in which signals are induced responsive to casing anomalies, and a secondary winding, conductor means connecting said primary winding between said cable conductor and a ground connection, and conductor means connecting one side of said secondary winding to ground and the other side of said secondary winding in series with said detonator device to ground. i

5. A collar locator device comprising a core element, a pair of magnets, with said core interposed in magnetic circuit between said magnets, a primary winding on said core for generating signals responsive to well casing anomalies, and a secondary winding on said core for connection in circuit with a perforating assembly detonator device, with said secondary winding having substantially fewer turns than said primary winding.

6. A collar locator device comprising a core element, a pair of permanent magnets, with said core interposed in magnetic circuit between said magnets, a relatively high inductance primary winding on said core for generating signals responsive to well casing anomalies, and -a relatively low inductance secondary winding on said core, for connection in circuit with a perforating assembly detonator device.

7. In bore hole apparatus, the combination of relatively high inductance magnetic induction conductor means adapted to be lowered into a bore hole for producing a signal indicative of a condition within the bore hole, a relatively low inductance magnetic induction conductor means magnetically linked to said relatively high inductance magnetic induction conductor means, a relatively low impedence electrical utilization circuit connected in circuit with Vsaid relatively lowinductance magnetic induction conductor means, and an electric circuit common to said utilization circuit and relatively high inductance magnetic induction conductor means and including a single electrical conductor extending to the surface of the earth, a source of fluctuating current, electric indicating means responsive to said signal, and electrical means for selectively connecting said source and said indicating means in said common electrical circuit.

8. In apparatus for performing operationsin cased bore holes, the combination of a tool assembly adapted to be lowered into a well, said assembly including casing collar locating means having a magnetic induction primary winding and a magnetic induction secondary winding, said secondary winding having lower inductance than said primary winding, said assembly including casing perforating apparatus having an electrical ring circuit connected in circuit with said secondary winding, a source of fluctuating current at the surface of the earth, electrical indicating means at the surface of the earth, and electrical circuit means including switching means for connecting said source and said indicating means selectively'to said 10 primary Winding.

References Cited in the le of this patentV Y UNITED STATES PATENTS 

